The demand for handheld and wearable electronic devices continues to grow. Examples of handheld electronic devices include mobile cellular telephones, imaging device (e.g., cameras), music devices (e.g., MP3 players), and devices that integrate the functionality of one or more of the just-mentioned devices. Examples of wearable electronic devices include eyeglasses that may integrate the functionality of an imaging device, a video display, and an Internet access terminal. An additional example of a wearable device includes a wrist-wearable device that may integrate the functionality of devices that monitor/record/transmit a user's physiological parameters (e.g., heart rate, blood oxygen level, restlessness during sleep) and/or geographic location. Wrist-wearable devices may additionally or alternatively integrate the functionality of mobile cellular devices with color displays. Many handheld and wearable electronic devices integrate with some form of wireless communication. Users expect new features, additional memory, and improved performance with each iteration of an electronic device. Moreover, users expect that their devices will remain the same size or be reduced in size despite the incorporation of new features, additional memory, and improved performance.
To reduce size, devices may be designed with an increase in transistor density and/or a decrease in the size of the die incorporated within the device. At least for protection and integration purposes, the die can be mounted into packages. To reduce package size, wire-bonding of die into packages has given way to flip-chip bonding. Package forms, such as the ball grid array, are also used to reduce overall size of the devices.
Vertical integration of die/packages has also helped to reduce the overall size of electronic devices. In vertically integrated designs, dies/packages may be stacked one atop the other. Examples of dies/packages stacked vertically include the package on package (PoP) structure. The PoP structure may be comprised of a vertical stack of ball grid array packages.
Another structure used for vertical integration is known as an embedded die substrate or embedded laminate substrate (referred to herein for consistency as embedded die substrate (EDS)). An EDS may employs a multiple layer substrate. To reduce vertical size, instead of mounting active die and/or active/passive components to the top of the multiple layer substrate, the active die and/or active/passive components are mounted within a cavity in the multiple layer substrate.
Use of EDS may reduce vertical size but difficulties remain in implementation. For example, in an EDS implementation, access to pads on a topside (e.g., first side) of a die from nodes adjacent to an opposite backside (e.g., second side) of the die may involve use of die that are costly to fabricate. It is therefore desirable, for example, to reduce the costs of die used in EDS implementations yet maintain access to pads on a topside of the die from nodes adjacent to a backside of the die.